Prospecção em fitopatógenos e avaliação de fontes de matéria orgânica sobre a supressividade da podridão radicular da mandioca

Abstract

The cultivation of cassava has great importance worldwide, it is the sixth largest crop production and expression of the planet. Brazil is the second largest producer in the world and this culture is the second largest national economic expression, with great social importance as it contributes to the survival of a significant portion of the low-income population as a source of income and food. This work aimed to make the first survey of fungi associated with root rot of cassava in Agreste of Pernambuco, to evaluate the effect of sources and levels of organic matter isolated and added to sandy soil under the suppressiveness of mycelial growth of Scytalidium lignicola and check the effect of levels and sources of organic matter incorporated into sandy soils inoculated with Scytalidium lignicola on the black rot of cassava cv. Father Antonio. Were collected plant material with symptoms and / or signs of disease in the Wasteland producing municipalities of Pernambuco: Jupi, Jucati, São João and Caetés. The frequency of isolation of the fungi was performed by plating method until pure culture isolation and identification. The second moment were the first two experiments was to evaluate the effect of extracts of organic materials (poultry manure, goat manure, cattle and earthworm castings) added to the culture medium potato dextrose agar (BDA) at concentrations (10 , 20, 30 and 40%) (v / v) and the second was to evaluate the effect of organic materials mixed with sandy soil with fountains and the same doses. The variables analyzed were: radial growth rate, mycelial growth inhibition and area under the curve of mycelial growth. After the results of the previous experiment was conducted a review of the effect of organic materials litter (CA) and goat manure (EC) incorporated into the sandy soil concentrations (10, 20 and 30%) (v / v). The variables analyzed were: Severity of disease, soil basal respiration, microbial biomass carbon samples, the chemical (pH, P, Na and K) and biochemical attributes and alkaline phosphatase and urease. The most prevalent fungi were tested for pathogenicity. We found a high diversity of fungi associated with root rot of cassava in rural Pernambuco. The prevalence of fungi associated with Fusarium root rot in cassava with symptoms from all areas of the municipalities of Jupi, Jucati and St. John and Scytalidium lignicola from areas of the Municipality of Caetés. Isolates that had prevailed in a high severity of cassava cultivate Branquinha. In test doses and sources on the mycelial growth of Scytalidium lignicola the source litter was the most effective in inhibiting the growth at a dose 40%, with an inhibition of mycelial growth of 69.75% only when the extracts were not autoclaved . Sandy soil with incorporation of sources and levels of organic matter were highly efficient in suppressiveness mycelial growth of S. lignicola. The treatments considered suppressive to black rot will grow dad Anthony EC were 10 and 20% and CA 20 and 30%. Being recommended for suppressiveness black rot of cassava caused by Scytalidium lignicola EC at doses of 10 and 20%.